The correlation between modified Phalen’s test and electrodiagnostic severity in carpal tunnel syndrome

Abstract

Objective: To evaluate 1) the diagnostic accuracy of modified Phalen’s test compared with the electrodiagnosis in diagnosis of CTS, 2) sensitivity of modified Phalen’s test in different electrodiagnostic severity, and 3) the correlation between the duration of positive modified Phalen’s test and electrodiagnostic severity.

Design: Retrospective cohort study

Methods: Three hundred and fifty-four patients were referred to do the electrodiagnosis at the Thammasat University hospital from 1 January 2014 to 30 April 2019. Rehabilitation doctor evaluated Modified Phalen’s test and electrodiagnosis. The electrodiagnostic protocol and diagnostic criteria for CTS used the recommendations by the American Association of Electrodiagnostic Medicine (AAEM).

Results: One hundred and fifty-three patients with 297 symptomatic hands were analyzed using the modified Phalen’s test and electrodiagnosis criteria. The diagnostic accuracy of modified Phalen’s test was: sensitivity 54.3%, specificity 76.9%, LR+ 2.4, LR- 0.6, PPV 86.9%, NPV 37.5%, and the area under ROC curve 0.66. Sensitivity in mild, moderate and severe CTS were 47.1%, 55.2%
and 63.0%, respectively. The correlation coefficient between the duration of positive modified Phalen’s test and the electrodiagnostic severity was -0.2. (P= 0.010)

Conclusions: The diagnostic accuracy of the modified Phalen’s test was fair in diagnosis of CTS. The sensitivity of modified Phalen’s test increased following the severity of CTS. There was no correlation between the duration of positive modified Phalen’s test and the electrodiagnostic severity.